DE2806672A1 - MEASURING ARRANGEMENT FOR THE FILLING STATE OF A LIQUID TANK - Google Patents

Description

RAINER-ANDREAS PAUL-ALEXANOER

Telefon0 8161/620 91 l / MUMCM O \ Λ / Λ ^ ΙΧΓΤΙ "-> Schneggstr.a-5, Postfach 172 £ Telex: 526547 pawa dl \ U Π NQ IN Ot VV AU KtK

Telegr. PAWAMUC-FREISING dipl-ing. DiPU-INQ-U-DiPL-WmTSCR-INQ. D-8050 FREISING / MÖNCHEN

Mr 16 EG 0101 2 / ko

Axel Egnell

Kungsgatan 20

440 30 MARSTRAND / SWEDEN

Measuring arrangement for the filling level of a liquid tank

The invention relates to a measuring arrangement for the filling level of a liquid tank.

Level measuring devices of various types are known, but all of these have known devices and arrangements have the disadvantage that they do not take into account the density or specific gravity of the liquid, and in many In this case, even ignore the gas or air pressure in the tank. As a result, if for example a ship has filled its tanks at a comparatively low temperature and then goes to warmer areas, the expansion space be filled in the tanks, and if these expansion spaces have been dimensioned too small, so expanded the liquid and overflows. The reason for such

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incorrect dimensioning and calculation is due to the fact that the pressure sensor near the bottom of the tank leads to a measurement display, which only corresponds to the pressure or weight of the column of liquid that is bearing on the sensor. Without knowing the specific gravity of the liquid, the filling level of the liquid cannot be calculated. If beyond that the specific gravity of the liquid also fluctuates with temperature changes, the information corresponds to the The specific weight of the supplier of the liquid is not always the same as that of the actually charged one Liquid, which further complicates the calculation of the required expansion space.

The invention is intended to avoid these disadvantages and to create a measuring arrangement of the type specified at the beginning. that is simple in structure and works independently without energy supply, so that a 100% explosion and Fire safety is achieved.

This object is achieved by the characterizing features of claim 1, while the subclaims are advantageous Developments of the invention have to the content.

Further details, features and advantages of the invention emerge from the following description of two exemplary embodiments based on the drawing. It shows

Fig. 1 schematically simplified and partially in section a measuring arrangement according to the invention, the tank up to maximum permissible filling level is filled,

FIGS. 2 and 3 show, on an enlarged scale, sections through the upper and lower pressure sensors, respectively.

Figures 4 and 5 are front and rear views, respectively, of the display device the measuring arrangement in a display position corresponding to the empty tank and

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6 shows an alternative embodiment of one according to the invention Measuring arrangement with electronic components for signal transmission.

In the drawing, 1 denotes a tank, for example a ship's tank, "which has tank walls 2, a tank bottom 3 and a tank cover 4". Arranged immediately above the tank bottom 3 is a first pressure sensor 5, which has a housing 6, on the underside of which a pressure cell 7 is provided. The pressure cell 7 has a pressure plate 8 to which a bellows 9 is attached, the pressure plate 8 being connected to a hydraulic double-acting pressure member 11 by means of a pressure rod 10 or the like Rods 13 are connected to one another and arranged on both sides of a support plate 12 which is fastened in the housing 6. Covering membranes 16, 17 of the pressure chambers 14, 15 are rigidly fixed against the support plate 12 by means of spacers 18, 19, in which channels 20, 21 are provided which each end in one of the pressure chambers 14 and 15, respectively. The channel 20 connects the pressure chamber 14 with an ascending line 22 in the form of a tube in the upper part of the housing 6, while the channel 21 connects the interior of the pressure chamber 15 with a second ascending, correspondingly designed line 23. The ascending lines 22 and 23 have a considerably larger cross-sectional area than the associated channels 20 and 21. The pressure chamber 14, the channel 20 and the line 22, like the pressure chamber 15, the channel 21 and the ascending line 23, each form a hydraulic system in which the ascending lines 22 and 23 are only partially filled with a hydraulic fluid. The interior of the pressure cell 7 is connected to the interior of the housing 6, which in turn is connected via a line 24 to the space above the maximum permissible fill level h _max in the tank 1. In order to protect the bellows 9 against corrosive attacks, the failure

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bellows 9 enclosed in an outer pressure cell like this From Fig. 3 it can be seen, on the od via a membrane. Like. The external pressure in the tank 1 acts and by means of a suitable liquid pressure transmission medium applied to the pressure plate accordingly.

The upper parts of the two ascending pipes or lines 22 and 23 are each connected to a line 25 and 26, respectively. which leads to a first display device 27 in the form of a transparent U-shaped tube 28, whose free leg ends open into a liquid storage vessel 29 and 30, respectively. In the U-tube 28 and partially filled also in the Liquid storage vessels 29 and 30 are provided with two non-mixing liquids of different colors, which form a defined dividing line against each other. On one of the legs of the U-tube 28 is a reading scale provided, which has display markings from 0 to 100, for example.

The pressure sensor 5 thus has a hydropneumatic measured value transmission system to the display device 27, with a change in the pressure in the liquid in the tank 1 on the Pressure cell 7 acts through the pressure chambers 14 and 15 to the Adjusts the liquid level in the ascending lines 22 and 23 accordingly. The columns of liquid in the ascending Lines 22 and 23 serve as displacement pistons in the subsequent Pneumsiik system, and those in the lines Air entrapped 25 and 26 proportionally transmits an increase or decrease in pressure into the liquid storage vessels 29 and 30, where this pressure leads to a corresponding adjustment of the dividing line in the liquid column in the U-tube 28 leads. The different heights of the liquid columns in the ascending lines 22 and 23 act like corresponding piston movements, whereby the product the piston or liquid stroke and the effective transverse

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sectional area of the respective ascending line 22 and result in the displacement volume.

In the upper area of the tank 1 and at a fixed distance below the highest permissible level h _max in the tank 1, two pressure sensors 32 and 33 are arranged in one unit, the pressure-sensitive surfaces of the pressure sensor located on the top and bottom of this unit in one mutual distance c (see. Fig. 1) lie. The pressure sensors 32 and 33 in the present embodiment also consist of pressure cells, the lower pressure sensor 32 being structurally identical to the pressure sensor 5 with the lower part of the housing 6 and the pressure sensor 33 being arranged in a mirror image on the top of the housing; For functionally corresponding parts of the lower pressure sensor 33, the corresponding reference numerals as for the pressure sensor 5 have therefore been chosen. The two pressure sensors 32 and 33 are rigidly connected to one another by means of push rods 10, 13 and 34 in the manner shown in detail in FIG. The interior of the pressure cells of both pressure sensors 32 and 33 is connected to the interior of the housing, which is connected via a line 35 to the space above the maximum permissible fill level ^ _13x . Ascending pipes or lines 36 and 37 of this structural unit are connected by means of lines 38 and 39 to a second display device 40, which also has a U-shaped transparent measuring tube 41, the free leg ends of which each open into a liquid storage vessel 42 or. The liquid storage vessels 42, 43 are partially filled with two non-mixing liquids of different colors, the dividing line between the two liquids forming an indicator line. A scale division is not absolutely necessary, but the display markings from 0 to 100 of the reading scale 31 are common to both display devices 27 and 40 and form the only reading that is required for display device 40.

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The pressure plates 44 and 45 of the pressure sensors 32 and 33 are dimensioned so that their effective areas are inversely proportional the height of the column of liquid on them, so inversely proportional to the distance a and b of the Pressure plate 44 or pressure plate 45 from the maximum filling

Stand height "K _n ^. When the tank 1 is filled with fresh water max

is, this exerts a pressure on the upper pressure sensor, which presses the dividing line from the range of the scale value 100 to the scale value 0 via the dark column of liquid in the U-tube of the display device 40. The hydropneumatic system is designed so that the displacement of the liquid column in the display device 40 from the marking 100 to the marking 0 corresponds to the distance c, i.e. the distance between the pressure plates 44 and 45 of the pressure sensors 32 ^ and 33, respectively 1 has risen to the level of the pressure plate 45 of the pressure sensor 33, this becomes effective and gives a pressure pulse in the opposite direction, which causes the dividing line in the liquid column in the display device to reverse at the mark 0 and return to the mark 100. The distance b from the pressure plate 45 to the maximum permissible level height h _jn is selected so that the maximum permissible level in the tank 1 is reached when the dividing line between the different colored liquids in the display device 40 has reached the marking 100. If the tank is now filled with diesel oil or seawater, for example, the dividing line between the liquids of the display device 40 is reversed below the marking, but this is of no interest since only the marking 100 serves as a level indicator. During the entire measurement, both pressure sensors 32 and 33 are influenced by the gas or air pressure in the space above the liquid level in tank 1, so that pressure compensation results, i.e. the measurement deflection is not caused by different air pressure.

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or the gas pressure above the liquid in the tank is adversely affected.

So that the weight of the various components of the pressure sensor such as pressure plates, connecting rods etc. does not affect the measurement result affect, the fluid pressure from the ascending line 23 and 37> which are connected to the pressure chamber 15, slightly higher than the corresponding liquid pressure from the ascending lines 22 and 36 so that a compensation results.

The dimensioning of the arrangement in adaptation to a given tank height is made by suitable selection of the effective pressurized surface of the pressure sensor 5, in which fine adjustment can be made ₅ that displacement bodies such as prismatic rods are inserted into the ascending lines 22 and 23 an increase in the stroke of the fluids acting like a piston, however, the desired stroke volume is maintained.

Since the signal transmission medium between the pressure sensors and the display devices is air under atmospheric pressurej, the measurement takes place independently and automatically as well as hydropneumatically with high accuracy. Since the columns of liquid in the display devices 27 and 40 have both a feed line and a discharge line, the measurement results are independent of temperature fluctuations.

In use, when filling the tank with a liquid, for example oil, the pressure sensor 5 exposed to an increasingly higher pressure, which the display device 27 in such a way influences that the liquid column, which is darker in the example shown in FIG. 1, rises from the marking 0 upwards = When the liquid in the tank reaches the pressure sensor 32 “so

if this is also pressurized, and if, for example, the distance c between the two pressure sensors 32 and 33 is 0.5 m and the distance between the pressure plate 44 of the pressure sensor 32 and the maximum fill level height h _{jnax is,} for example, 1 m, the refilling can take place of the tank 1 up to exactly the maximum permissible filling level h _jnax , since the measuring display of the display device 40 can be followed during the last meter of filling. The filling is ended when the liquid column in the reading leg of the display device 40 has covered the way from the marking 100 down to the marking 0 and back up to the marking 100. In this position, the specific gravity of the liquid can be read on the second display device 27, the specific weight being 0.95 in the example of FIG.

With the measuring arrangement explained, the maximum permissible level ^ _{3x of} the liquid in the tank 1 can be read on the display device 40 independently of the specific weight of the liquid, the specific weight of the liquid being readable on the display device 27 at the same time. The weight and volume of the tank's contents can be easily calculated using the ship manufacturer's capacity table, which is available for each tank and therefore contains the information in percentages of the height.

As can be seen from Fig. 6, an electronic or combined hydropneumatic-electronic measured value via- carried out in cases in which the risk of explosion is very low or negligible. At this Embodiment, either pressure sensor types according to the previous exemplary embodiment can be used as the pressure sensor

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or conventional electronic pressure sensors, for example inductive, capacitive or piezo-electric work. In the example of FIG. 6 electronically operating pressure sensors may be used, the first Pressure sensor 5 'is attached to the bottom 3 of the tank or in its immediate vicinity, a second pressure sensor 32' in a distance S "below the maximum permissible level

h ^. ,,, and a third pressure sensor 33 'at a distance S "under jnax l

is located half of the highest permissible level \ _iax ; Finally, a fourth pressure sensor 47 is arranged in the immediate vicinity of the upper cover of the tank 1 above the liquid wedge level. The pressure sensors 5 ¹ , 32 ', 33' and 47 generate electrical signals a, b, c and d which are applied to an electronic measurement data converter 46 and are proportional to the ambient pressure in the area of the corresponding pressure sensors. The output signal d of the pressure sensor 47 is thus proportional to the gas or air pressure G in the tank 1, which prevails above the liquid surface. The signals c, d and a of the pressure sensors 33 ', 32' and 5 'are proportional to the liquid level above the corresponding pressure sensors, to the density of the liquid and to the gas or air pressure in the tank 1, which acts on the liquid surface and directly on this pressure sensor works when these are not influenced by the liquid in the tank.

The measured data converter 46 consists in the present embodiment of input differential amplifiers, the first input differential amplifier F- receives the signals d and c from the pressure sensors 47 and 33 'and subtracts the signal d from the signal c, so that a compensation for the gas pressure G in the tank results, and the difference _{signal is amplified by a factor f 1} , so that an output signal k ₁ results. The signals b and d from the pressure sensors 32 and 47 are applied to a second differential _{amplifier F 2} , the signal d being subtracted from the signal b so that a compensation for the gas

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pressure G in tank 1 results, and after which the difference signal is amplified by a factor f "and results in _{an output signal k o.} The output signals k- and k ₂ thus result in k ₁ = f _Λ (c - d) and k ₂ = f ₂ (b - d). If the corresponding values are set for the signals, i.e. d = G, c = S- + G and b = Sp + G, then k- = Ir ₁ (S ₁ + G-G) and k _{2 result for the output signals} = P ₂ (S ₂ + GG). \ -Jerw. the maximum fill level is thus to be displayed independently of the density of the liquid, so the gain _{factors f, are grounded.} and f "selected so that the output signals k ^ and k ^ are the same when the liquid has reached the predetermined maximum fill level h _max . If the following applies: k ^ = k ₂ , then accordingly also f ₁ (S ₁ + G - G) = f ₂ (S ₂ + GG), i.e.:

Thus, the gain factor f _{1 should be} a constant f ₂ S ₀ Zs ₁ . The signals k ₁ and k ₂ influence a third differential _{amplifier F «f} in which the signal k _{2 is} subtracted from the signal k ₁ and the resulting difference is amplified to an output signal ko, which is fed to a first display device 40 ', which is analog or can work digitally.

When the tank 1 is empty, the display device 40 ′ displays an initial value 100. When the tank 1 is filled and the liquid level reaches the pressure sensor 32 ', the gauge falls to the value 0. When the liquid level reaches the pressure probe 33', the gauge movement is reversed, and when the gauge 100 is reached, it becomes indicated that the maximum fill level h _{max has been} reached and the filling of the tank 1 has ended.

The pressure sensor 5 ¹ , which is arranged at the bottom of the tank 1, applies a signal a to a fourth differential amplifier F * in the measured data converter 46. The output signal k ^ from the difference

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amplifier F ₄ consists of the difference between the signal a and the signal d, so that a compensation of the gas pressure G takes place in the tank 1, and is then _{amplified with a factor f 4} , which is chosen so that the display deflection of a second digital or analog display device 27 'displays the specific gravity of the filled liquid. If necessary, the signal k. _r, which corresponds to the specific weight of the liquid, can be fed to a further signal processing circuit, not shown in detail, in which the value corresponding to the measured volume of the tank can be added for different liquid heights, with corresponding data in the load capacity tables supplied by the manufacturer (bearing table ) or filling tables are available. A display device calibrated according to the weight units, for example tons, following this signal processing circuit can thus display the weight in tons for a predetermined fill level.

The invention makes it possible that the filling of the tank exactly at a predetermined fill level regardless of the density of the liquid and changes in the liquid level in the vicinity of the maximum fill level h _jnax, for example as a result of the effects of heat and the resulting density changes, canceled and the fill level as well the density can also be easily displayed. An alarm system can easily be provided and generate a warning signal if the maximum fill level \, _{ax is} exceeded for any reason. Furthermore, the total weight of the loaded liquid can be read off either by means of appropriate tables or directly in the manner explained above on a further display device.

The electronic pressure sensors can easily be arranged so that their pressure-sensitive surfaces are substantially

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lie vertically so that possibly adhering residue or the like does not affect the measurement result. When a If there were oil residues in the hydraulically operating pressure sensors, such a weight increase could be complete can simply be compensated by the fact that the vent screws on the liquid storage vessels of the display devices be solved.

As the above description shows, the invention is not restricted to the embodiments shown. For example, the hydraulic pressure sensors could be combined with electronic data transmission and data display be used.

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Claims (7)

PATENT LAWYERS RAINER-ANDREAS PAUL-ALEXANDER Telephone 0 8161/6 2091 I / II LJ MCM D \ Λ / ΛΓ ^ Ι / ΙΓη Schneggstr. 3-5, P.O. Box 172i Telex: 526547 pawa d MJ Π IN L IN & VV AU I \ L. K r. PAWAMUC-FREISING dipl-inq. dipl-ing. u. Dipl.-Wirtschafts-inq. D-8050 FREISING / MÖNCHEN Mr 16 EG 0101 2 / st Axel Egnell
Kungsgatan 20 30 Marstrand / Sweden Claims , J measuring arrangement for the filling level of a liquid tank, characterized in that a first pressure sensor (5; 5 ') is provided in the immediate vicinity of the bottom (3) of the tank (i) or directly on the bottom (3), that a second and third Pressure sensors (32, 33; 32 ', 33') are arranged at different fixed heights (a, b; S, S) below the maximum permissible level (^ _x ) that a device (47) for compensating for changes in the air or Gas pressure (G) is provided in the tank, that a first display device (27 _f 27 ') or signal processing unit for displaying or processing the measurement data from the first pressure sensor (5; 5 ¹ ) is provided, and that a second display device (40; 40' ) or signal processing unit for displaying or processing the difference between the measurement data of the second and third pressure sensors (32; 32 · or 33; 33 ¹ ) is provided. 2. Measuring arrangement according to claim 1, characterized in that the first pressure sensor (5) is a double-acting ORIGINAL INSPECTED 809835/0639 j naokqsreioht | Pistons, double-acting pressure cells or pressure chambers (14, 15) or the like in a housing (6), the piston rod (1O) or the like acted upon i £ t, Vina that the inside of the housing (6) and the back of the pressurized surface (8) are under the gas or air pressure barely above the liquid level in the tank (1). 3. Measuring arrangement according to claim 1, characterized in that the second and the third pressure sensor (32, 33) are combined into one unit, which has a double-acting Piston, a double-acting pressure chamber arrangement or the like. In a housing (6), with a continuous Piston rod (34) or the like of the piston or the pressure chamber arrangement with one end with the underside a pressure-sensitive, from the .liquid pressure in the Tank acted upon surface (45) and the opposite end with the top of a pressure-sensitive, from the liquid pressure in the tank (1) acted upon surface (44) cooperates that the interior of the housing (6) and the facing inner sides of the pressure-sensitive surfaces (44, 45) the gas or air pressure in the area Above the liquid level in the tank (1) are exposed, and that the size of the pressure-sensitive Areas (44, 45) of the second and third pressure sensors (32 and 33, respectively) are inversely proportional to the height of the liquid column which act on the respective pressure sensor (32, 33) when the tank (1) is full. 4. Measuring arrangement according to claim 2 or 3, characterized in that the responsive to positive and negative pressure changes Pressure chambers (14, 15) of the double-acting Piston or the double-acting pressure chamber arrangement of the pressure sensor (5, 32, 33) are each connected to an ascending line (22, 23 , 36, 37), preferably designed as a tube, the liquid stroke and the liquid stroke volume in the respective ascending line, for example are preferably kept adjustable by displacers which can be inserted into the ascending line. 5. Measuring arrangement according to claim 1, characterized in that each pressure sensor by means of lines (25, 26 or 38, 39) for a pneumatic medium, each with a display device (27, 40). connected, which is a transparent, U-shaped Has measuring tube (28, 41), the free leg ends of which to 'a liquid storage vessel (29? 30 resp. 42, 43) are connected, the transparent U-tubes and partially the liquid storage vessels with two non-mixing liquids of different colors are filled, so that between the liquids a defined dividing line forms which on the first display device (27) the specific Indicates the weight of the liquid when the tank is full and the second display device (40) indicates the highest permissible fill level (h). 6. Measuring arrangement according to claim 1, characterized in that the measurement data (b, c) from the pressure sensors (32 ', 33'), which are arranged at fixed distances (S ₁ , S) from the liquid level, in input differential amplifiers (F, F ₂ ) can be processed so that the measurement data (d) from a pressure sensor (47) arranged below the top cover of the tank (1) above the maximum permissible filling level (h) is dependent on the measurement data (b "c) of the at fixed intervals (S, S ₂ ) arranged pressure sensor (32% 33 ') must be deducted so that the output signals (k "k) from these amplifiers (F ", F ₀ ) with a factor f" or ltd I f _{p are} amplified, where f is the quotient of the distances (S / S), that the output signals k and k can be fed to a third input differential amplifier (F "), in which the output signal k _{2 is} subtracted from the output signal k, and that this Difference (k-k) corresponding output signal (k ₃ ) is fed to a display device (40 *). 7. Measuring arrangement according to claims 1 and 6, characterized in that the measurement data (a) from the pressure sensor (5 ') arranged on the bottom (3) of the tank (i) are connected to an amplifier (F ₄ ) in which the measurement data (d) of the pressure sensor (47) arranged below the cover of the tank (1) subtracted from the measurement data (a) of the bottom-side pressure sensor (5 ') and amplified with a factor f. and displayed in a second display device (27 *). 809835/0639